Inkjet printing technology is used in many commercial printing devices to provide high-quality image printing solutions at a reasonable cost. One type of inkjet printing known as “drop on demand” employs an inkjet pen to eject ink drops through a plurality of nozzles onto a print medium, such as a sheet of paper. The nozzles are typically arranged in arrays on one or more printheads on the pen, such that properly sequenced ejection of ink from the nozzles causes characters or other images to be printed on the print medium as the pen and the print medium move relative to each other. In a specific example, a thermal inkjet (TIJ) printhead ejects drops from a nozzle by passing electrical current through a heating element to generate heat and vaporize a small portion of the fluid within a firing chamber. In another example, a piezoelectric inkjet (PIJ) printhead uses a piezoelectric material actuator to generate pressure pulses that force ink drops out of a nozzle.
A continuing challenge with inkjet technology is maintaining the health of the nozzles. Printheads are typically capped or sealed in a high humidity environment during non-use to reduce drying of ink at the printhead nozzles. However, factors related to “decap” (i.e., the amount of time inkjet nozzles remain uncapped and exposed to ambient environments during use), such as evaporation of water or solvent can increase drying of the ink, resulting in clogging or partial blockage of the nozzles, or the formation of ink crust and/or viscous plugs in the nozzles. Clogged and blocked nozzles can alter the weights, velocities, trajectories, shapes and colors of ink drops being ejected from the nozzles, all of which can negatively impact the print quality of an inkjet printer.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.